i40e: fix netdev_stat macro definition

The old xxx_NETDEV_STAT() macro was defined long before the newer
rtnl_link_stats64 came into being, and just never got updated.  Since we're
using rtnl_link_stats64 in other parts of the driver, we should use it
here as well.  We've just been lucky that the field definitions are the
same sizes.

Change-ID: I19fc71619905700235dcdf0d3c8153aec81d36de
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>